This invention relates to winged implements in which the wings are biased by a hydraulic downpressure circuit to pivot toward the ground during operation to provide force onto the ground working tools so that they better penetrate hard ground to the set working depth.
An earlier form of downpressure system shown in Flexi-coil's U.S. Pat. No. 5,687,798 uses PRRV (pressure reducing-relieving valve) as controls in the downpressure circuit. A related system is shown in Flexi-coil's patent application (U.S. Ser. No. 08/891,204, corresponding to Canadian 2,210,238.
Recent tractor designs include hydraulic systems on the tractors that are CCLS (closed center load sensing) systems. These systems attempt to maintain a set flow volume through each of the tractor valves, when open. This volume can be set by the operator. The tractor hydraulic pump is controlled such that it will increase the system pressure until the flow volume at each of the open valves is satisfied. This system allows for efficiency to be gained from previous systems in which the pump volume output was reduced only after full pressure capability had been reached. Circuits connected to the tractor that have PRRV controls, will only accept flow when the PRRV senses a requirement for flow in the circuit connected downstream of the valve. A tractor having CCLS controls will attempt to deliver flow in any case, and the tractor pump will raise the pressure to the system maximum. This not only diminishes the efficiency of downpressure circuit which is causing the problem, but also diminishes the efficiency of any of the circuits being operated because the tractor control system introduces pressure drops at each valve to maintain only the set flow.